1. Field of the Disclosure
The present application relates to a liquid crystal display panel. Also, the present application relates a method of manufacturing a liquid crystal display panel.
2. Description of the Related Art
With the development of an information society, the requirements for display devices used to display images have been increased in a variety of manners. As such, flat panel display devices being thinner and lighter weight compared to cathode ray tubes (CRTs) of the related art are being actively researched and manufactured. The flat panel display devices include liquid crystal display (LCD) devices, plasma display devices (PDPs), organic light emitting display (OLED) devices and so on. Among the flat panel display devices, the LCD devices are now widely being used because of features such as small size, light weight, slimness and low power drive.
A twisted nematic mode LCD device is one of the LCD devices being mainly used up to the present. The twisted nematic mode LCD device applies a voltage between two electrodes each formed on two substrates, in order to drive liquid crystal directors which are aligned between two substrates in such a manner as to twist by an angle of 90° degrees. However, the twisted nematic mode LCD device has the disadvantage of a narrow viewing angle.
To solve the disadvantage of the TN mode LCD device such as a narrow viewing angle, new mode LCD devices are being actively researched. As such, an IPS (in-plane switching) mode LCD device and a FFS (fringe field switching) mode LCD device are proposed as new mode LCD devices.
FIG. 1 is a cross-sectional view illustrating the drive principle of an IPS mode LCD device according to the related art. FIG. 1a is a cross-sectional view showing liquid crystal molecular alignment in a turned-off state of the LCD device. FIG. 1b is a cross-sectional view showing liquid crystal molecular alignment in a turned-on state of the LCD device.
Referring to FIG. 1, the IPS mode LCD device includes a first substrate 301, a second substrate 302 and a liquid crystal layer 306. The first and second substrates 301 and 302 are disposed to face each other. The liquid crystal layer 307 including liquid crystal molecules 307 is interposed between the first and second substrates 301 and 302. A plurality of pixel electrodes 341 and a plurality of common electrodes 343 are formed on the first substrate 301. The liquid crystal molecules are displaced by an electric field which is generated by a potential difference between the pixel electrode 341 and the common electrode 343, in order to display an image.
When the LCD device is turned-off, the potential difference between the pixel electrode 341 and the common electrode 343 is zero, and then the liquid crystal molecules 307 are aligned in a front-rear direction as shown in FIG. 1a. Similarly, in a normally black mode, the liquid crystal molecules 307 are aligned in the front-rear direction and shield light which is applied a backlight unit (not shown) so that a black image is displayed.
On the contrary, when the LCD device is turned-on, different potentials are applied to the pixel electrode 341 and the common electrode 343, and then an electric field indicated by arrows 398 in FIG. 1b is generated by the potential difference between the pixel electrode 341 and the common electrode 343. The electric field indicated by the arrows enables the liquid crystal molecules 307 to be aligned in a left-right direction. In other words, in a normally white mode, the liquid crystal molecules 307 are aligned in the left-right direction and transmit light applied from the backlight unit (not shown), thereby displaying an white image.
This IPS mode LCD device provides a wide viewing angle but has a problem with brightness. To address the problem with brightness of the IPS mode LCD device, the FFS mode LCD device has been proposed.
FIG. 2 is a cross-sectional view illustrating the drive principle of a FFS mode LCD device according to the related art. FIG. 2a is a cross-sectional view showing liquid crystal molecular alignment in a turned-off state of the LCD device. FIG. 2b is a cross-sectional view showing liquid crystal molecular alignment in a turned-on state of the LCD device.
The FFS mode LCD device shown in FIG. 2 has the same structure as the IPS mode LCD device except that the pixel electrode and the common electrode are formed in different layers. As such, the components of the FFS mode LCD device of the same configuration as those of the IPS mode LCD device will be referred to by the same reference numbers and names. Also, the description of the FFS mode LCD device overlapping with the IPS mode LCD device will be omitted.
Referring to FIG. 2, the FFS mode LCD device further includes an insulation film 305. The common electrode 343 is formed between the substrate 301 and the insulation film 305. The pixel electrodes 341 are formed on the insulation film 305.
When the LCD device is turned-off, the potential difference between the pixel electrode 341 and the common electrode 343 is zero, and then the liquid crystal molecules 307 are aligned in a front-rear direction as shown in FIG. 2a. Similarly, in a normally black mode, the liquid crystal molecules 307 are aligned in the front-rear direction and shield light which is applied a backlight unit (not shown) so that a black image is displayed.
On the contrary, when the LCD device is turned-on, different potentials are applied to the pixel electrode 341 and the common electrode 343, and then an electric field indicated by arrows 308 in FIG. 2b is generated by the potential difference between the pixel electrode 341 and the common electrode 343. The electric field indicated by the arrows 308 enables the liquid crystal molecules 307 to be aligned in a left-right direction. In other words, in a normally white mode, the liquid crystal molecules 307 are aligned in the left-right direction and transmit light applied from the backlight unit (not shown), thereby displaying an white image.
In this manner, the FFS mode LCD device forces the pixel electrode 341 and the common electrode 343 to be disposed in different layers, unlike the IPS mode LCD device. As such, the FFS mode LCD device can generate not only an in-plane electric field but also a vertical electric field and accurately align the liquid crystal molecules. In accordance therewith, the FFS mode LCD device can provide higher brightness compared to the IPS mode LCD device.
In the FFS mode LCD device, the pixel electrode 341 and the common electrode 343 can be replaced with each other in the formation position. For example, the pixel electrodes 341 can be formed between the substrate 301 and the insulation film 305, and the common electrode 343 can be formed on the insulation film 305.
The narrower the distance between the pixel electrodes in the FFS mode LCD device is, the higher the operation efficiency of the liquid crystal molecule can become. However, it is difficult to narrow the distance between the pixel electrodes below a critical value due to hindrances in the process of manufacture, such as a masking tolerance caused by a diffraction characteristic for light. Due to this, transmittance of the FFS mode LCD device cannot be enhanced.